High resolution background maps can be obtained through the integrated Chart Downloader plugin see GSHHS High Resolution Background Use with Watchdog Landfall alarms and WeatherRouting plugins for land detection.
Path to this dataset is stored in the BasemapDir configuration key in opencpn.ini. As long as it points to Contents/SharedSupport/gshhs/, replacing the content of Contents/SharedSupport/gshhs/ makes OpenCPN use it. If BasemapDir points somewhere else, it is not going to be used.
In case GSHHG data is pointed to as a chart folder, it is detected and BasemapDir is changed to point to that location.
Basemap is always displayed, regardless of chart groups.
Keep your GSHHG dataset up to date using ChartDownloader, please.
Background Map (GSHHS Low Res) - Installed, used by Opencpn for the initial rough background map.
Crude resolution basemap is included in the installation package. By default, under macOS, installed in Contents/SharedSupport/gshhs/ subfolder of the application bundle.
For MacOS it is installed in Contents/SharedSupport/gshhs/subfolder of the application bundle.